In the castle of Bratislava overlooking the River Danube, the US president emerged from a two-hour summit with Mr Putin to state that the rule of law, a free press, a viable opposition and protection of minorities were central and universal attributes of democracy.

"I was able to share my concerns about Russia's commitment in fulfilling these universal principles," Mr Bush said.

He qualified the criticism later by stating that Mr Putin had assured him that the Kremlin was fully committed to democracy.

Despite a raft of US-Russian agreements on nuclear security, arms exports, counter-terrorism and trade and economic issues, the post-summit press conference by the two leaders was dominated by the issue of the fate of democracy in Russia.

In the closing speech of his four days of summitry with European, Nato and Russian leaders in Belgium, Germany, and Slovakia, Mr Bush hailed the democratic and pro-western upheavals in Ukraine and Georgia, former Soviet republics which the Kremlin still views proprietorially and where it opposed the democratic victors.

Mr Bush also said that democracy would ultimately prevail in Belarus, Russia's anti-western neighbour, and in Moldova, the poorest country in Europe and the only one governed by a communist party. It goes to the polls

Over the past four years, Mr Bush has been a strong supporter of Mr Putin after famously declaring at their first meeting that he had peered into the soul of the former KGB officer and discovered a trustworthy partner. But his second-term mission to expand freedom worldwide faced a big test yesterday given the perception that Mr Putin has been rolling back the rights and liberties of Russians.

Mr Putin has been accused of bullying opposition and the media and asserting Kremlin authority over legislators. Domestic criticism is rare, though yesterday a former prime minister, Mikhail Kasyanov, said Mr Putin's Russia was on the wrong track and democratic values such as an independent judiciary and media and a free business climate had not been allowed to flourish.

The Kremlin chief, who appeared unusually stiff and dour during the press conference, responded robustly to the suspicions about his rule, declaring that Russian democracy had already passed the point of no return.

Russia, he said, had opted for democracy 14 years ago, not to do anyone else's bidding but for its own sake. "This is our final choice and there can be no way back ... Any kind of turn towards totalitarianism would be impossible."

Under Mr Putin, Russia is commonly described by analysts as a "managed" or "controlled" democracy and Mr Putin has in the past argued that Russia's authoritarian history makes it difficult for full democracy to flourish.

Last night Mr Putin contradicted his own previous arguments. "We are not going to invent any kind of special Russian democracy," he said.

Mr Putin also indicated that the discussion over Russian freedom had dominated the summit. "We discussed these issues at length, face to face, just the two of us."

But in his opening statement describing the summit, Mr Putin did not mention that discussion once, nor did he mention the word democracy. Mr Bush, by contrast, made his most pointed criticism not in response to journalists' questions, but in his opening remarks. Mr Bush said Russia "should be a strong and viable partner" of America, indicating that the US-Russian relationship is no longer as strong as it has been in the years since 2000 when first Mr Putin then Mr Bush came to power.

Before yesterday's summit, US senators and congressmen, as well as influential opinion-formers, have been urging Mr Bush to "get tough" on Russia where Mr Putin is seen to have been concentrating power in the Kremlin and eroding many of the democratic gains of the past 15 years. But Russian politicians and commentators have been bristling about being lectured by the US and warning of a mini-cold war.